Grounding device for vehicles



April 21, 1942. D. c. WARE 2,280,327

GROUNDING DEVICE FOR VEHICLES Filed Jan. 29,. 1940 Patented Apr. 21, 1942 UNI'TED` STATES PATENT OFFICE GROUNDING DEVICE FOR VEHICLES David Curtis Ware, Laguna Beach, Calif.

Application January 29, 1940, Serial No. 316,183

8 Claims.

This invention relates to a device for grounding vehicles and relates more particularly to a static grounding device for rubber-tired tank trucks andthe like conveying inilammable fluids, explosives, etc. A general object of this invention is to provide a quiet, dependable .and long Wearing vehicle grounding device ofthe character mentioned.

Tank trucks used to transport gasoline and other inflammable and explosive products are usually equipped with a grounding attachment to carry away the electricityggenerated by the agitation of the liquid in the metal tanks. Such grounding devices are essential on all rubbertired tank trucks carrying explosives or highly inflammable fluids as the discharge of the static electricity in the tanks may result in an ,explosion. The grounding device now most generally used consists of a length of chain suspended from the rear of the truck to drag along the road and thus carry off the static electricity. The lower links of the chain, or the blade sometimes attached to the chain, wear away rapidly and there is always the hazard that the chain will not be replaced or lowered to again comtact the ground, before a dangerous'static charge builds up in the truck. Ihe chain links striking the road surface produce a great many sparks and fluid leaking from the truckv may be ignited by these sparks and cause burning or explosion of the truck and its contents. Further, the chain draggingalong the road produces aloud and very disagreeable noise and for this reason certain communities have prohibited the travel of tank trucks on their roads when equipped with such IA tioned that may be readily manually adjusted to adapt it for use on vehicles of different types, heights, etc.

Another object of this invention is to provide a grounding attachment embodying a novel grounding 'wheel adapted to run along the road in trailingy relation to the truck and mounted in such a manner that it may caster in response to all changes in d-irection of movement of the truck.

Another object of this invention is to provide a grounding attachment of the character mentioned embodying a novel tire for the grounding wheel formed of rubber, or the like, to be noiseless and long wearing, and embodying embedded electrical conducting parts for contacting the road surface to carry away the static electricity.

Another object of this invention is to provide a grounding attachment of the character mentioned embodying dependable and eilicient spring means for maintaining the road contacting conducting wheel in cooperation with the road, which means is adjustable as conditions may require.

A furtherobject of this invention is to provide a grounding attachment of the character mentioned that may be readily folded or retracted to form a small, compact unit'clear of the ground.

The .various objects and features of my invention will be fully understood from the following detailed description of a typical preferred form and application of the invention, throughout which description reference is made to the accompanying drawing, in which:

Fig. l is a side elevation of the rear portion of a typical tank truck showing the grounding attachment of the present invention in its operative position on the truck. Fig. 2 is an enlarged detailed sectional view taken substantially as indicated by Aline 2-2 on Fig. l showing the fork and wheel in plain view. Fig. 3 is an enlarged vertical detailed sectional view taken as indicated by line 3-3 on Fig. 2. Fig. 4 is a fragmentary vertical detailed sectional View taken as in# dicated by line 4 4 on Fig. 2, with certain parts in side elevation, and Fig. 5 is a fragmentary detailed sectional View of the wheel and its tire.

The device of the present invention may be attached to vehicles of various types and to vehicles carrying different products, it being a feature of the invention that the device is adaptable for use on practically all classes of vehicles. In the drawing I have shown the device applied to the back of a truck T of the type employed to carry gasoline, etc., it being understood that the invention is not to be construed as limited or restricted to -the particular form or application about to be described.

The improved grounding device of the invention may be said to comprise, generally, a foldable and longitudinally extensible arm I0 to be pivotally secured to the truck T, a fork II pivotally carried by the arm I0, a rotatable conducting wheel I2 carried by the fork I I, a resilient conducting tire I3 on the wheel I2, and regulable spring means I4 acting on the arm I0 to yieldingly maintain the tire I3 of the wheel in engagement with the road surface.

The arm I is an elongate structure intended to be secured to the rear of the truck T to extend downwardly and rearwardly therefrom and to swing or pivot about a substantially horizontal axis. In accordance with the invention the arm I0 is formed to be foldable and to be longitudinally extensible and contractible to adapt the device for use on trucks varying greatly in height and type. In the construction illustrated the arm I0 comprises two spaced substantially parallel outer members I5 and two spaced inner members I6. As shown, the arm members I5 and I6 are elongate flat parts. The inner members I6 slidably bear on the inner surfaces of the outer members and have longitudinally spaced openings I1. Tubular ferrules I9 are suitably set or secured in the openings I1. The upper ends of the inner members I5 may be connected by an integral transverse web I8 so that the members move in unison. The inner members I5 are proportioned to extend outwardly or rearwardly beyond the outer members I5. The upper ends of the outer arm members I5 are connected by a tubular ferrule or spacer 2D.

The invention provides novel means for securing or locking the inner arm members I6 in the selected adjusted positions relative to the outer members I5 and for connecting the pairs of members for relative pivoting. Each outer member I5 has a transverse opening 22 for registering with a ferrule I9. Leaf springs 23 are arranged at the outer sides of the members l5 and are tied together and held in place by a bolt 2I passed through the openings 22 and the registering ferrule I9. The outer or free ends of the springs 23 carry inwardly projecting pins 24. The pins 24 extend through openings 22a in the members I5 and are of sufficient length to extend into selected ferrules I9 of the inner members I6. Handles or knobs 25 are provided on the springs 23 so that the pins 24 may be readily withdrawn from the ferrules I9. When the pins 24 are withdrawn from the ferrules 2I the members I6 may be pivoted relative to the members I5 about the axis of the bolt 2I to permit folding of the device as will be later described. To extend or contract the arm Il) the bolt 2| is removed and the members I6 are shifted longitudinally relative to the members I5. The members I6 may be moved to bring a selected ferrule I9 into registration with the openings 22 whereupon the bolt 2I is replaced and the springs 23 are allowed to move the pins 24 into the ferrule I9. With the bolt 2I replaced and the pins 24 entered in the ferrule I9 the members I6 are effectively locked or latched against movement relative to the members I5.

Bracket means is provided to attach the arm I9 to the truck T so that the arm may project downwardly and rearwardly from the truck and may swing about a substantially horizontal axis. A bracket 26 is suitably xed to the rear portion of the truck T to be in contact with a metal part or conducting part of the truck. Spaced ears 21 project rearwardly from the body of the bracket 25 and the upper portions of the arm members I5 enter between the ears. A pivot pin 2B is passed through horizontal openings 29 in the ears 21 and a horizontal opening 30 in the upper portion of the arm Il] to pivotally attach the arm to the bracket 26. Suitable pins or keys 3l may hold the pin 28 against displacement. It will be seen that the arm I0 secured to the truck T by the bracket means may freely swing about a substantially horizontal axis and may normally extend downwardly and rearwardly from the truck.

The fork II serves to carry or mount the ground wheel I2 and is pivotally attached to the outer end of the arm ID so that the wheel may swing or caster in response to changes in direction of movement of the truck T. As illustrated the fork II may comprise a tongue 32 formed of plate stock, or the like, and spaced rearwardly extending spring arms 33. The spring arms 33 are suitably replaceably attached to the tongue 32. The rear portions of the arms 33 are curled or rolled to form aligned substantially horizontal bearings 34.

The invention provides novel adjustable means for attaching the fork II to the arm I0 to swing or pivot about a substantially vertical axis. This means includes a bearing block 35 having a substantially vertical opening 35 passing a king pin 31. The pin 31 extends downwardly from the block 35 to pass through an opening 38 in the fork tongue 32 and has a head 39 on its lower end engaging the under surface of the tongue. It is preferred to provide the pivotal mounting of the wheel fork II with shock absorbing means. A nut 4I) is threaded on a reduced upper portion of the pin 31 and a cup 4I is clamped under the nut 40 to telescope downwardly over the upper portion of the block 35. A similar cup 42 is arranged on the pin 31 to engage against the fork tongue 32 and to telescope upwardly over the lower portion of the block 35. Coiled compression springs 43 are housed in the cups 4I and 42 to bear between the end walls of the cups and the ends of the bearing block 35. The springs 43 yieldingly resist vertical shifting of the pin 31 and the fork II relative to the block 35.

The bearing block 35 is adjustably secured to the outer end of the arm I0 in such a manner that the pin 31 may be brought to a substantially vertical position with the arm I0 adjusted to different angular positions as required by the attachment of the device to trucks of different types and heights. The means for adjustably securing the block 35 to the arm I9 includes a horizontal pin 44 arranged through registering openings in the outer ends of the members I6 and the block 35. The pin 44 connects the block 35 with the arm I0 for adjustment or pivotal movement about a substantially horizontal axis. Radial flanges 45 project from the block 35 and lie against the inner sides of the arm members I6, and each flange has a threaded transverse opening 45. An arcuate series of transverse openings 41 is provided in each arm member I6. The openings 41 are arranged in concentric relation t0 the axis of the pin 44 and are positioned t0 successively come into registration with the openings 46. Screws 48 are adapted to be passed through corresponding selected openings 41 to be threaded into the openings 46. The bearing block 35 may be pivoted or adjusted relative to the arm IU to bring the pin 31 to a substantially vertical position, and the screws 48 may then be passed through the openings 41 and threaded into the openings 4E to secure the block in its adjusted position.

The wheel I 2 is rotatably supported in the fork i to metal contact with the wheel I2.

ablerimfl-angefSG is provided to hold the tire I3 II to be in trailinglrelation to the truck4 and:

to have its tire I3 contact the road surface.I vThe wheel- I2 -is prefer-ablyfalmetal structure to effectively -conduct electricity iand is supported in the fork` I-I to 'be 4'in electrical conducting relation thereto;y An axle v50 rotatably carries the wheel I2 va-I'idLhasits endvportionsreceived in the bearings-3419iy they fork 'I-I. y'The'wheel `I2 maypof course; be provided with i suitablev anti-friction bearings and the' bearings l-when -employed are suchthat electricity is readily conducted from the axle 50 tor the wheel.n UA suitable mud guard or A.fender 5I may be provided on the fork I-I to extendfoverlthe upper portion yof the wheel I2. It will be observed'ithatf the -axis of rotation of the' wheel I2 isoffsetfrearwardly from the axis of thev pivot pin 31so that the wheel may readily caster about the axis ofthe pin.v

The 'tire I3 of the wheel I2 forms the earth or roadfengaging element of the grounding device and is of novel construction to assurefthe full and effective-dissipation of the static electricity that may-be generated in the truck T. The tire I3 is an annular member Yformed of rubber, rubber composition, synthetic-rubbery or the llike,`with or without fabric reinforcement. The tire I3 preferably has v-a wide-flat tread-so that it will not catch or wipe in railway tracks and the like. It is afeature of the invention that the tire I3 embodies electrical conducting elements. screening is cast or embedded in the tire I3 to be exposed-at the internal 'surface and the external periphery of the tire. There may be several disc-like layers of metal screening elements 52 provided y-in the tire I3 to have their edges at thefinner and outer surfaces of the tire. The

Metal Wheel-I2 is provided with a pitched periphery 53 and a radial annular flange 54 at `the high end of its peripheral surface. The inner side of the tire I3 is providedfwithtwo outwardly diverging surfaces 55 and onesurface- 55 isvadapted to contact the wheel surface 53.l AThis brings one or more of the wire screening elements 52 in metal A detachon the vwheel I2. The ange 55 may be held against aside of the wheel. I2 by screws 51. The innerside of the*detachableminrfiange 56 has a tapered annular lip 58 for engaging one of the sloping surfaces 55 of the tire I3. metal'. screen elements. 52 have direct metal to metal Vcontact with the lip 58. i It will be seen that the yielding. or resilient tire I3 may operate or roll along roads surfaced in Various manners with little or no sound, and` thatthe metal screeny ing elements 52 of the tire maintain the grounding device in electrical contact with the earth at'all times.

The means I4 serves to urge the arm I2 down` wardly to yieldinglyhold the tire I3 of the wheel I2 in cooperation with the road surface. The spring means I4 includes an extensible tension spring 60 anchored to the bracket 26 and connected with the arm I0. The outer end of the spring 60 may be suitably hooked through a l may be varied to provide the desired or required downward force on the arm I0. The spring Certain of the ings 58.

a pin'IiI suitablylsecuredkto `thei arm membersv I5. Arcuateiseriesof openings '68 aire provided in the'-A bracket ears-21 andLaLpinBS 'may be ar-V ranged in selectedfpairsor setsi-of aligned open- The upper porticnlof the 'springf is engaged 'over'` the. Spin AIii). iBy Ia'rrangingrY the .pin 69 in differentfopenings 68 `thespring 65 maybe adjusted .to zurgesthexarmzzfl downwardly,. as required.

The'.v several .parts` of the .'igroundingifdevice, with: the` exceptionof the/:tire .I3, areiformed of electrical.conductingx'materialf suchfas iron or steel, andthe bracketL26 is securedv to a frame part Lor grounding: part of. the 'truck..T so that static electricity that .maybe generated in the truck'. flows `through .thezfgrounding ldevice. As above described, the metal `screening kelements 52 of the' tire -I3 carry this 'electricity to the earth or road surface.

In using the device the bracket 26 is suitably secured to the truck so that the arm I0 may project downwardly and rearwardly. The arm I0 may be extended or contracted to adaptthe device for use on trucks of different types or heights.

35 about the pin 44 to the correct or selected' position. The screws 48 are replaced to secure the block 35 in the adjusted position. The screw 62 may -be adjusted to give the spring 60 the' desired laction and, if necessary, the pin 69 may be adjusted to vary the action of the spring 66. It will be seen that the device is fullyy adjustable to adapt it for practically any operating conditions.

When the truck T is in operation the Wheel I2 rolls along the road in trailing relation to the truck and its tire I3 contacts the road surface. Any static electricity that may be generated in the truck T is conducted through the device to the wheel I2 and the metal screening elements 52 carry the electricity to ground. The .Wheel carrying fork II is supported to pvot on the pin 31 so that the wheel I2 may swing or casterV in response to changes in direction of movement of the truck and the fork arms 33 may flex when the wheel runs on uneven pavement, etc. The arm I0 is pivotally supported by the pin 28 so that the entire device may pivot relative to the truck when the truck travels over uneven ground, etcgand the pivoted arm II) automatically conditions the device -for different load conditions of the truck.

When the grounding device is not required or when it is desired to back the truck T into a confined space the grounding device may be folded into a compact unit at the back of the truck. This may be done by freeing or disconnecting the springs 60 and 66 and then retracting the pins 24 from the ferrule I9 so that the fork and the arm members I6 may be pivoted upwardly. This upward pivoting of the members I6 and the fork I0 brings the wheel I2 to a position adjacent the back of the truck T and the raised parts may be suitably hooked `or secured in the elevated position where they are clear of the ground and in close relation to the truck back.

means LI4 rniay-furtherf.include alleafv spring 5S With the device secured to the truck T and the arm I0 adjusted as found necessary,v

I have shown a hook 80 on the truck T for engaging in an eye 8| on the fender 5I to retain the device in its folded position.

Having described only a typical preferred form and application of my invention, I do not wish to be limited or restricted to the speciiic details herein set forth, but Wish to reserve to myself any variations or modifications that may appear to those skilled in the art or fall Within the scope of the following claims.

Having described my invention, I claim:

1. A grounding device for a vehicle comprising an arm member, means for securing the member to the vehicle to extend downwardly and rearwardly therefrom and to pivot about a horizontal axis, a bearing on the rear end of the member, a groundengaging conducting wheel, a fork rotatably mounting the wheel and carried by the bearing to swing about a generally vertical axis, and means for adjusting the bearing about a substantially .horizontal axis so that the axis of swinging of the fork may be made substantially vertical With the member at different angles.

2. A grounding device for a vehicle comprising an arm member, means for securingV the member to the vehicle to extend downwardly and rearwardly therefrom and to pivot about a horizontal axis, a ground engaging conducting wheel, a fork rotatably mounting the wheel, bearing means connecting the fork with the arm member to swing about a generally Vertical axis, and shock absorbing means associated with the bearing means.

3. A static grounding device for a vehicle comprising a bracket attachable to the vehicle, an extensible and contractible arm secured to the bracket to extend rearwardly and downwardly therefromy andl to swing about a substantially horizontal axis, a ground engaging conducting wheel, a member rotatably mounting the wheel,

a bearing pivotally supporting said member and secured to the arm for adjustment with respect thereto whereby the member may be made to swing about a generally vertical axis with the arm in different angular positions, means for securing the bearing in selected adjusted positions, and releasable means for holding the arm against elongation and contraction when adjusted to the desired length.

4. A grounding device for a vehicle comprising a structure attachable to the vehicle to extend therefrom and to be in electrical conducting relation thereto, a conducting wheel in electrical conducting relation to the structure supported by the structure to rotate, an annular resilient tire on thewheel for running on the road surface, and a plurality of axially spaced discs of wire mesh embedded in the tire to have their inner edges exposed at the interior of the tire to contact the wheel and to have their peripheries exposed at the periphery of the tire to be in electrical contact with the road.

5. A grounding device for a vehicle comprising a structure attachable to the vehicle to extend therefrom and to be in electrical conducting relation thereto, a conducting wheel in electrical conducting relation to the structure supported by the structure to rotate, a resilient tire on the Wheel for running on the road surface, a detachable rim flange on the wheel retaining the tire on the wheel, and a disc element of metal screening occupying a generally radial plane in the tire and exposed at the interior of the tire to contact the wheel and exposed at the periphery of the tire to be in electrical contact with the road.

6. A static grounding device for a vehicle comprising a bracket attachable to the vehicle, an extensible and contractible arm secured to the bracket to extend rearwardly and downwardly therefrom and to swing about a substantially horizontal axis, a ground engaging conducting wheel, a member rotatably mounting the wheel, a block swingably supporting the member, and means adjustably mounting the block on the arm whereby the axis of swinging of the member may be made substantially vertical with the arm in different angular positions, said means including a pin supporting the block on the arm for pivoting about a substantially horizontal axis, and means for holding the block against pivoting in any one of a plurality cf different positions.

'7. A static grounding device for a vehicle comprising a bracket attachable to the vehicle, an arm having its upper end pivotally supported by the bracket to swing about a horizontal axis, the arm including two members related for relative pivotal movement about a transverse axis whereby the arm is foldable, releasable means for holding the members against relative pivoting when the arm is in the operative position, a road contacting conducting wheel, a carrier rotatably supporting the wheel, and means mounting the carrier on the lower end of the arm to pivot about a generally vertical axis.

8. A static grounding device for a vehicle comprising a bracket attachable to the vehicle, an arm pivotally supported from its upper end on the bracket to swing about a horizontal axis, the arm including two members related for relative pivotal movement about a transverse axis whereby the arm is foldable1 releasable means for holding the members against relative pivoting when the arm is in the operative position, a road contacting conducting wheel, a carrier rotatably supporting the wheel and carried by the arm to pivot about a generally vertical axis, and means for holding the device elevated when the arm is folded.

D. CURTIS WARE. 

